Capacitive Door Sensor with Reference Electrode Distance Compensation
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Solution Overview
Problem
Existing sensor systems for protecting movable objects, such as motor-driven doors or flaps, face challenges in accurately distinguishing between signal changes caused by the closing of the door and the presence of objects due to capacitive sensor signal variations, leading to unreliable object detection.
Innovation Solution
The integration of a separate movable electrode and a control unit that generates and evaluates transmission signals to derive distance information between the capacitive sensor and the electrode, allowing for improved object detection by compensating for signal changes caused by the door's closing state, thereby enhancing the reliability of capacitive object capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is used to detect objects near movable objects, then object detection capability is provided, but the sensor cannot reliably distinguish between signal changes caused by door closure and signal changes caused by object presence
Solution Approach 1:
The evaluation of capacitive sensor signals is segmented into two distinct components: a first evaluation component processes the reception signal to detect objects, while a second evaluation component determines distance information between the sensor and a reference electrode. This segmentation allows independent optimization of each evaluation aspect and enables the system to distinguish between closure-induced signal changes and object-induced signal changes by comparing results from both components.
Solution Approach 2:
A reference electrode is introduced as an intermediary element that serves as a stable reference point for distance measurements. This reference electrode, positioned at a known location relative to the movable object, mediates the measurement process by providing a consistent capacitive coupling that varies predictably with distance. The second evaluation component uses this intermediary reference to calculate distance information that compensates for signal variations caused by door closure, thereby improving the reliability of object detection.
2Ease of operation
If the capacitive sensor is mounted on a movable object such as a tailgate, then the sensor can detect objects in the closing gap, but the reception signal changes solely due to tailgate closing without object presence
Solution Approach 1:
The system implements feedback by continuously monitoring the capacitive coupling between the sensor and the reference electrode and using this information to adjust the object detection threshold. The second evaluation component calculates distance information from the reception signal, and this distance information is fed back to the first evaluation component to compensate for signal changes caused by tailgate closure. This feedback mechanism enables the system to maintain high detection precision despite the movable mounting position.
3Reliability
If distance information is derived from the reception signal, then signal changes due to door closure can be compensated, but the system complexity increases
Solution Approach 1:
The evaluation of object presence and the determination of distance information are merged into a single integrated evaluation process. Both the first evaluation component (object detection) and the second evaluation component (distance determination) process the same reception signal from the capacitive sensor, eliminating the need for separate sensing hardware. This merging approach reduces overall system complexity while maintaining the reliability benefits of distance-based compensation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly improves the detection of objects by providing reliable distance information, enabling the differentiation between door closure-induced signal changes and object presence, resulting in more accurate and sensitive object detection for motor-driven doors or flaps.
Implementation Method 1
a sensor system for protecting movable objects, in particular motor-driven doors or flaps, having at least one capacitive sensor
Implementation Method 2
The control unit is designed to generate a transmission signal for the at least one capacitive sensor and to evaluate a first reception signal from the at least one capacitive sensor
Data Source
AI summary
A sensor system for protecting movable objects, in particular motor-driven doors or flaps, having at least one capacitive sensor and having at least one control unit. The control unit is designed to generate a transmission signal for the capacitive sensor and to evaluate a first reception signal therefrom. At least one further electrode is provided, wherein the capacitive sensor and the further electrode are movable relative to one another. The control unit has an evaluation arrangement which evaluates a second reception signal from the further electrode, and the evaluation arrangement is designed to derive an item of information relating to the distance between the capacitive sensor and the further electrode from the second reception signal.